Stand Alone Reverb
Moderators: pompeiisneaks, Colossal
Stand Alone Reverb
Can I use any 5-8K OT to drive the tank in a stand alone reverb?
Re: Stand Alone Reverb
I don't think so, I don't think it is the same as a regular OT.
The part number is 125A12A but I can't find a replacement for that exact number.
The common driver is 125A20B or 022921
Those have a 25K primary and 8 ohm output.
The part number is 125A12A but I can't find a replacement for that exact number.
The common driver is 125A20B or 022921
Those have a 25K primary and 8 ohm output.
Tom
Don't let that smoke out!
Don't let that smoke out!
Re: Stand Alone Reverb
It just depends on the tube you are using and the impedance of the tank, it's the same as designing any output stage, except instead of a speaker, you're using the tank (but the tubes and transformers don't know that!)
So with a 12AT7 or a 12AU7, the 50K load is pretty good (25K into two triodes equates to 50K apiece). If you are building a standalone unit with a 6V6, EL84, 6K6, etc., then sure, a 5 to 8 load should work just fine. Especially if you aren't overdriving the reverb driver, the load can be very flexible or forgiving.
So with a 12AT7 or a 12AU7, the 50K load is pretty good (25K into two triodes equates to 50K apiece). If you are building a standalone unit with a 6V6, EL84, 6K6, etc., then sure, a 5 to 8 load should work just fine. Especially if you aren't overdriving the reverb driver, the load can be very flexible or forgiving.
Life is a tale told by an idiot -- full of sound and fury, signifying nothing.
...in other words: rock and roll!
...in other words: rock and roll!
Re: Stand Alone Reverb
If you were planning to use a paralleled 12AT7, you can just order the standard Hammond replacement for Fender amps, which is 22K8||8. If you want to experiment with other impedance ratios, the Hammond 125 series gives you taps you can connect to get everything from 22K5 to 3K into 8 ohms. They're not specifically SE (no air gap), but it really won't matter in this application. That does raise the other possibility with the 125s using a 12AT7 or 12AU7: wire the two triodes to run push-pull instead of SE. You'll get a lot less stray noise shooting out of the reverb tranny.